THE MOUSE AND ITS ALLIES 325 



weight of over 100,000 kilogrammes. It is, indeed, the 

 largest living animal. Although whales in general are 

 partly adapted to an aquatic life, they still retain the 

 essential mammalian qualities. They breathe air which 

 passes to the lungs and is expelled again through the 

 nostrils, which are placed high up on the head. The 

 " blowing ' of the whale is the forcible expiration of 

 moisture-laden air, which becomes visible by condensation, 





FIG. 300. Oca, the killer whale. After True. 



just as our own breath does on a cold day. The young 

 are doubtless born in the water, but the breeding habits 

 are poorly known. The various Cetacea have diverse 

 feeding habits. All are predaceous. The toothed whales 

 feed on larger animals, the whalebone whales on floating 

 fish, Crustacea, medusae, and squids ; their whalebone is, 

 indeed, merely a strainer to let the water pass out of the 

 mouth while the solid masses are retained. 



The order Ungulata 1 includes a large number of animals, 



1 unyula, hoof. 



